1. Field of the Invention
The present invention pertains to a combined process for the recovery of minerals and salts from non arable lands such as occur in alkali and alkaline soils while reclaiming and improving the land for agricultural purposes. More particularly, the invention relates to a combined process for mining and improving land for agricultural purposes and for the transitional development of the land from predominantly mining to predominantly agricultural purposes by the utilization of subterranean drain pipe to collect subterranean water from a recharge area and percolated waters from a swale or discharge area which incorporate dissolved salts and minerals which are mined from the collected water through chemical and physical treatments before the water is either discharged into the river or returned back to the surface of the land for topical application at either the recharge or discharge area to allow further circulation and percolation of the water through the land to dissolve and remove further soluble salts and minerals.
The invention contemplates the gradual return of non arable lands from land mining to agricultural purposes in a developmental progress in which a selection of plants and crops are utilized to assist in the transition from mining to agricultural stages of the invention. The water applied to the surface of the discharge area and the subterranean water from the recharge area is purified and recirculated and is utilized in conjunction with salinity measurements of the soil in the swale or discharge area as an indicator of the progress of the land in the mining and land reclamation aspects of the invention.
2. Description of the Prior Art
In recent years, over large portions of the States of Montana, South Dakota, North Dakota and the Canadian provinces of Alberta, Saskatchewan and Manitoba saline seeps have been developing to convert agricultural lands into non arable lands. Since the 1940's the saline seeps that have been developing in the Great Plains have resulted in about 80,000 acres of land being lost to production. The U.S. Soil Conservation Service estimates the rate of saline seep expansion is over 10% a year, which estimate does not include lands adjacent to the seeps that have been rising in salinity and have been exhibiting erosion effects from saline springs and saline damage due to run-off drainage from the seeps.
The problem of saline seep is distinct from the alkaline soil or the "salt flats" that have been historically alkaline soils that were the result of poorly drained areas in which the soil salts collected over the ages. The saline seep problem is a recent phenomena resulting from agricultural practices in which large acreage areas are allowed to remain fallow and the nature of crop plant roots in grain farming. Farm crops have rather short tap roots in comparison with indigenous plants of the plain which had tap roots that extended between 2 and 12 ft. into the soil. The replacement of the indigenous plants with wheat and other forms of grain in combination with fallow farming practices do not stem the downward seepage of water into the sub surface water tables resulting in a rise in the level of the water table. The indigenous plants of the Plains prevented the percolation and seepage of water down into the sub surface and the rise of the water tables and as a result, prevented lateral movement of salt laden water to form saline seeps on other areas. Traditional agricultural crops that have replaced the indigenous plants of the Plains also are not as resistant to the salinity of the swale or discharge area which forms a saline seep for which most vegetables, cereal crops, alfalfa, clover, and hay are unable to survive because of the high salt concentrations in the seep.
Saline seep water cannot be collected and discharged into streams because the alkalinity kills fish, endangers the dissolved oxygen in the water which favors toxic blue green algea and causes disease producing organisms to proliferate in the salt charged saline seep solutions. Saline seep water not only kills aquatic life but also is attributable to the deaths of birds and animals that depend on the river water. Consequently, it is not possible to collect and discharge these saline seep waters into the rivers and waterways.
The solution to the problem of saline seep has not been forthcoming and the closest available prior art pertains to methods for leaching or recovering ores from land utilizing leaching processes and the concentration of underground brine by solar evaporation. The prior art such as U.S. Pat. No. 2,563,623; U.S. Pat. No. 4,017,309; and U.S. Pat. No. 1,908,876 all pertain to various leaching and ore recovery techniques. These inventions utilize leaching, concentration, and recirculation but are significantly different than the present invention as these processes do not seek to return the land to an arable condition nor do these processes employ subterranean drainage for the purification of the water to return the land to arable condition.
In U.S. Pat. No. 3,966,541 a process for recovering chemicals such as chlorides, sulfates, carbonates, and borates from alkaline metals from underground brines is provided by utilizing a pond for solar evaporation of the water to concentrate the brine. In U.S. Pat. No. 3,966,541 the process concentrates and extracts these chemicals from areas such as the Mojave Desert where subterranean waters are collected and concentrated for subsequent removal of salts and minerals from the water but the land is not returned to arable condition nor is underground drainage utilized in a combined process to purify water and reclaim land for agriculture purposes. In U.S. Pat. No. 3,966,541 the testing of salinity of the soil in relation to the salinity of the combination of terranean and subterranean waters is not utilized nor does the prior art system employ water purification in the mining of the minerals of the present invention.
In U.S. Pat. Nos. 2,486,512 and 1,895,324 methods for promoting the growth of vegetation and irrigation systems are disclosed. These systems for promoting growth of vegetation and providing for irrigation do not provide for mining or the modification of non arable land to arable lands. The prior art patents alone or in combination do not teach or suggest the staged development of land from a mining use to agricultural use as is provided in accordance with the present invention.
The combination mining and land reclamation method of the present invention removes minerals and salts in a mining process which purifies the water and then discharges the water into a river or returns the water to the land for further mining operations. Since the return water can be applied to the surface of the land at either the recharge area or the discharge area the water can be completely or partially purified to suit the particular land conditions encountered. The combined method of mining and reclaiming land further contemplates periodic measurement of the salinity of the soil conditions in the discharge or swale in comparison with the periodic sampling of the subterranean collected water to determine whether the source of salinity is primarily from the recharge or discharge area. Where the recharge area is primarily responsible for the salinity of the subterranean waters the collected subterranean water may only be partially purified and returned to the recharge area to allow mining to continue without significantly interfering with the agricultural uses of the swale to control or provide the staged return of the land to an arable condition for agricultural purposes. The present invention not only assists in the elimination and control of saline seeps but more importantly in combination with the mining aspects of the invention makes the recovery, purification, and recirculation of the water economically justifiable while at the same time providing an existing drainage system to insure the maintenance of the land in the future for agricultural uses.